Electron sources employing vacuum ultraviolet radiation and nonreactive photocathodes to replace hot filaments for ion formation in both quadrupole and magnetic mass spectrometers will be designed, constructed, and tested on each type of instrument. New photocathodes will be developed and used. Operation of an ion source at pressures from 1 to 700 torr will be investigated so that electron attachment and ion exchange can be used to form ions for mass analysis. Prototype ion sources will be installed in quadrupole and magnetic mass spectrometers and evaluated for usual analytic purposes. Final engineering design for use with a popular quadrupole and a popular magnetic mass spectrometer will be developed. (5)